AbstractHealthy volunteers in phase 1 clinical trials contribute to the development of safe drugs and other biologics and accept risks and burdens without anticipated health benefits from participation. Although emerging data have shown that healthy volunteers are influenced by risk, some still worry that financial incentives lead them to take on unreasonable risk. Yet little is known about healthy volunteers' preferences and how they make choices about enrolling in research studies.METHODS:We surveyed 654 healthy volunteers at the end of their participation in a phase 1 Pfizer trial in the United States, Belgium, and Singapore to examine their reported willingness to enroll in studies of different types, with various procedures, and with possible side-effects.RESULTS:The majority of respondents were willing to join many kinds of studies, but fewer were willing to participate in first-in-human vaccine studies or studies of psychiatric drugs than in other study types. With regard to procedures, a substantial proportion were unwilling to participate in studies that involved invasive procedures, such as a lumbar puncture (45.4%) and bone marrow biopsy (42.3%), but willing to participate in studies with less invasive procedures such as a computed tomography scan of the heart (86.8%), magnetic resonance imaging (87.4%), and skin allergy testing (86.8%). Although there was some variation by gender and region, the majority were willing to participate in studies with side-effects like pain (80%) or nausea and vomiting (64%), but only a minority were willing to join if the research drug would result in their having a one in a million chance of death (34.4%), a small chance of kidney damage (16.7%), or influence how their mind works (23.2%; Figure 4).CONCLUSION:Our results suggest that healthy volunteers are willing to participate in a wide range of types of phase 1 clinical trials, and express preferences for low risk and familiar studies and study procedures, preferences which are partially affected by offers of payment.